POLA PERKEMBANGAN ASEKSUAL DAN SEKSUAL PADA HEWAN

POLA PERKEMBANGAN ASEKSUAL DAN SEKSUAL PADA HEWAN:

POLA PERKEMBANGAN ASEKSUAL DAN SEKSUAL PADA HEWAN

oleh : Mega Sirnawati 

1. Asexual development patterns in the Animal

Asexual reproduction is reproduction without mating sex cells (gametes) and the structure

Reproduction in Animals Invertebrates.

Can occur sexually (involving sex cells) and asexually (not involved)

Reproduction Asexual / vegetative cover:

• Fragmentation is the separation of one part of the body which can then grow and develop into new individuals. Reproduction of an organism in which the body broken into two parts or more, then each part will grow into new individuals are the same as its parent. Fragmentation event depends on the ability of regeneration of the tissue or organ repair capacity has been lost

• For example planaria sp and Asterias sp

(How to breed planaria sp. (Flatworms). Children who have formed from the stem cell division (fragmentation). Since there is no sex cells are involved it is called asexual reproduction.)

• Budding / bud / gemmulae the formation of a bulge on one side and pried the animal's body develop into new individuals. Examples of animals Euspongia Acropora sp and sp.

• Fission is cell division in stem cells and the result will develop into new individuals. Dibedakanmenjadi 2 is binary fission, for example in multiple fission in bacteria and viruses.

• Sporulation is the formation of spores in the spore cell indukdan will eventually develop into new individuals. For example in Plasmodium sp.

• parthenogenesis, namely through the establishment of new individuals without the fertilized egg cell. For example a male honey bees, male ants and grasshoppers.

• Paedogenesis the formation of new individuals directly from the larval / nimpha. For example in Class trematode / worms Fasciola hepatica and the suction is Clonorchis sinensis.

2. Pattern of Sexual Development in Animals

Reproduction in Vertebrates

• Class Pisces is the ovipar and external fertilization, ovovivipar and viviparous. Reproductive organs including testis, vas deferens, the hole urogenitalia for males and for females is the ovary, oviduct and urogenitalia hole.

• Class Amphibia is with external fertilization. Reproductive organs include the testes, vasa efferentia and kloakauntuk males and for females is the ovary, oviduct and cloaca.

• Class reptiles is by internal fertilization. Reproductive organs include the testes, hemipenes, vas deferens, epididymis, and cloaca. For females the ovaries, oviduct and cloaca.

• Class Aves is with internal fertilization. For the male reproductive organs, namely testis, vas deferens and the cloaca. For the female covers the left ovary, oviduct, and cloaca.

• Class mammals is by internal fertilization. Male reproductive organs include the penis, vas deferens, testicles and anus. For the female include the ovaries, oviduct, uterus and anus. Has a system called the menstrual phase of the estrous uterus and complex types. Included in this group are people

GROWTH PATTERN IN ANIMALS

1. Fertilization

            Fertilization or fertilization (singami) is a fusion of two gametes to form nuclei or nucleated cells to form a single cell (zygote) or nuclear fusion. Usually involves the incorporation of the cytoplasm (plasmogami) and the unification of the nuclear material (kariogami). With meiosis, the zygote is formed from the most fundamental characteristic of the sexual cycles of eukaryotes, and basically that's fused gametes are haploid. When both motile such as in plants, the fertilization is called isogami, when different in size but similar in form it is called anisogami, if one is not motile (and usually larger) called Oogami. This is a typical way in some plants, animals and most fungi. In most gimnofita and all antofita, gametnya not berflagel, and pollen tube involved in the process of fertilization.

Fertilization in animals

• External Fertilization (typical in aquatic animals): gametes are expelled from the body before fertilization.

• internal fertilization (typical for adaptation to life on land): the sperm is inserted into the female reproductive area which was followed by fertilization. After fertilization, the fertilization of the egg membrane to form a block further sperm entry. Sometimes it is necessary only for the sperm activates the egg.

• Fertilization in vitro (English: in vitro fertilization) is a technique in which fertilization of the egg (ovum) is fertilized outside the woman's body. IVF is one method to overcome fertility problems when other methods did not work. The process consists of the hormonal control of ovulation, the removal of eggs from the ovary and fertilized by the sperm cells in a liquid medium.

2. Cleavage zygote

A. Phase division (cleavage)

Cleavage or cleavage, or also called segmentation, occurs after fertilization. The zygote divides repeatedly to consist of dozens of tiny cells, called blastomeres. Division that could include all parts, can also only a small fraction of zygotes. This division occurs in mitosis, although sometimes also followed by a continuous nuclear division with no intervening cytoplasm.

Field division

Field direction taken by the mitotic division when the zygote has continued to be a lot of cells, called a field division. There are four kinds of divisions, namely:

1) Meridian, past the animal and vegetal pole axis.

2) Vertical, straight through since the animal pole to vegetal pole axis does not pass aimal and vegetal.

3) equator, perpendicular to the animal-vegetal pole axis and midway between two poles.

4) latitudinal, parallel to the equatorial plane dengfan.

Variety - there are 2 kinds of cleavage, namely:

A. Holoblastik

Is a division of the entire region zygote. Found in eggs and mid lecithal homolecithal. Divided into two, namely:

a. Holoblastik regular

A division which took place on a regular basis both in the cleavage stage meupun - cleavage stage. Found in Asterias (starfish), Amphioxus, and Anura (frogs).

Cleavage through the field perpendicular meridian, terbentukalah 4 equal cells, then past the latitudinal field, above the equatorial plane. Formed 8-cell, 4 cell next to the smaller so-called micromere, and four lower cells called macromore.

The fourth division over the fields serantak meridian which divides the two to eight cells. Cell 16 is formed consisting of 8 and 8 macromore micromore. After the division through latitudianal field, above and below the equator in serantak didang.

In the frog, when the thick layer of yolk that cleavage of the new macromore take a long time to reach the end of the vegetal pole. Finally terbentukalah blastomore consisting of 32 cells. Of the 32 cell divides to form the meridian through the field of 64 cells. At the end there is gumpaalan enlarged cleavage, which consists of about 70 cells, shaped like a pear called a morula. Morula was massive, it means the blind and not hollow.

In the frog is not clear form the morula blastomere. Because blastomere consists of dozens - pulh barangsung cell cavity formed in the center of the increasingly large. The cavity was filled with fluid.

b. Holoblastik irregular

An unequal division occurs at different times pembelahanya zygote. Found in mammals.

Latitudinal division through the field just above the equator. The zygote divides into two cells next to the pole of the smaller animal. Then the next division meridian through the field, but only during micromere vegetal pole. There was a level 3 followed micromere cells, through the meridian field as well. Formed tingakat 4 cells. Cleavage occurs at the macromere so tertbentuk one of the 5 cell and 6 cell. Micromere divides to form one of the 7 cell and another cell to form level 8.

The next division is not in unison, and finally formed blastomere consisting of 60-70 cells that form massive clumps, called a morula.

2. Meroblastik

Is the only division in the zygote in a small animal pole, excepting that the germinal disc and the yolk a little. Cleavage begins through a field meridian, forming stacks of cells in germinal disc region of about 12 cells 8sel middle and edge of the cell was still associated with the yolk below, on the edge of the cell is largely off the yolk dasri except the very edge. At this time the egg reaches the uterus, and is covered by the albumen and shell.

Blastomere chicken is called taking the morula, ie when the disc germnal a division that has not been established with the yolk slit underneath. Furthermore the division can not be followed.

At the time of embryo cells of the center will continue to have a mitotic division, to amount to 64 cells, and consists of 3 layers. Horizontal slit, called pembelahann cavity, just below the middle cells. Separate the cells from germ cells was another disc that does not have cleavage. Cell - the cell edge, is located on the outskirts of the germinal disc. Seluruhya cells was cut from the yolk below. Syncytium, connecting the cells - the cells below the edge of the yolk.

Cell - cell division is not perfect pinggor experience in sebelahy bordering the yolk, thus forming a separate lot without the cell nucleus - a separate cell (cytoplasm and cell membrane itself does not form). The core of many of these scattered towards the yolk below. Areas that contain many nuclei are called periblast network.

On Amphibious, fertilization occurs outside the female body (external fertilization). Zygote develops into an embryo in several stages. Morula is formed after 3-7 hours after fertilization, the blastula forms after 18 jamsetalah fertilization, and gastrul; a formed after fertilization. After about 84 hours, it appears the tail. A few days later about six days, the embryos hatch into larvae, called tadpoles. Tadpoles initially have three pairs of external gills. In a further development after nine days beyond the gills replaced by internal gills. Formed 12 days after the gill cover and the rear legs appear after about two to three months.

Once the tadpoles about 3 months or more will undergo metamorphosis. Further development of the organ is the lung begin to grow and evolve, the intestine becomes shorter, the gills of the decline, and finally the tadpoles develop into frogs.

3. Blastulasi

Blastula during embryonic development.

While the morula cells have a continuous division, forming a cavity in the center, which grew larger and filled with fluid. Embryo that has a cavity called a blastula. Blastula is an advanced form of the morula which continues to have cleavage. Blastula form marked by a change in the holding cell pelekukan irregular. Fluid contained in the blastula cells called Blastocoel. Blastrulasi the process of blastula formation.

Look at the shape and arrangement of blastomernya blastula is divided into:

1) Coeloblastula

Spherical, also called a round blastula. Derived from eggs and mediolechital homolechital. That homolechital division is experiencing a regular holoblastik (Amphioxus).

2) Discoblastula

Berebntuk flat discs called blastula. Derived from eggs that had homolechiutal holoblastik irregular cleavage, and the egg dividing megalichutal meroblastik. Blastula is above the yolk or food distributor network. On reptiles, aves and monotremata blastula called germinal disc.

Blastomere consists of two parts, namely:

a. Embryo tissue, the tissue will grow into embryos.

b. Periblast network, a network that delivers food from the yolk below.

Embrioblast or clumps of cells in the embryo will grow into. While tropoblast will distribute food from the parent uterus.

At the blastula there are two main areas, called:

a) epiblast, the blastomere that is located next to the upper or animal pole region.

b) Hypoblast, the blastomere that is located next to the bottom or the vegetal pole region.

On most of the growing blastula epiblast ectoderm (outer skin), while the growing hypoblast endoderm (the skin).

• Amphioxus

Epidermal ectoderm would be fostered by some bear the epiblast (micromere). Dorsal neural ectoderm in the form of a crescent, located to the lower epidermis of the area would ectoderm. Notochord will also be a crescent on the dorsal, located beneath the ectoderm would be nervous. Would be a crescent ventral mesoderm, ectoderm would be located below the epidermis and the dorsal side of the crescent. Will be developed over a layer of hypoblast endoderm (macromere), fill the bottom of the blastula.

• Frogs

Epiblast will cover areas of the epidermis and the neural ectoderm would, mesoderm and notocord. While hypoblast will be going to the endoderm. Epidermal ectoderm will fill most of the large crescent-shaped epiblast.

Neural ectoderm and notocord will be located together and crescent above. Will be located next to the crescent notocord mesoderm, which later will determine the left and right embryo. Mbryo will fill the entire hypoblast at the very bottom of the blastula.

• Aves

Epiblast will be bakl ectoderm, mesoderm and notocord. Will be derived from the hypoblast endoderm, the cells grow and spread down into the blastocoel cavity.

Epidermal ectoderm will fill the area that would be the anterior embryo epiblast layer. Neural ectoderm will be located in the posterior crescent etoderm epidermis. Would notocord and prechorda in posterior neural lectoder, is going in the posterior mesoderm epiblast layer.

• Mammals

In the polar regions more active animal divide, resulting in thickening. Thickening occurred at a series of sek into blastocoel displacement, menmbentuk hypoblast layer. So that becomes epiblast cells in clumps. Cavity below the hypoblast becomes archenteron cavity. Epiblast will develop will ectoiderm, notochord and mesoderm. Hypoblast will grow endoderm.

4. Gastrulation

Embryonic development at the gastrula.

Accompany the growth rate and the blastula is called gastrulation occurs, the embryo called the gastrula. Gastrula is formed by a continuation of the blastula pelekukan her more real and has a layer of embryonic body wall and body cavity.

At this level there is a process dinamiasi areas will be forming tool on the blastula, and dideretkan arranged according to the shape and body composition of species in question. The term is derived from the gastrula gastrum or gastric (stomach), because at this level would be terentuk cavity of the digestive tract. This is called gastrocoel cavity or archenteron.

In the process of gastrulation occurs continuously and perbayakan cell division, cell movement also occurred in the effort to organize and lined them according to individual body shape and composition of individuals of the species concerned.

Epiboli movement (melingkup) occurs in the outer embryo that will take place on ctoderm epidermis and nerves. Great movement will take place according to the anterior posterior axis of the body. While the move will mesoderm and endoderm, ectoderm epiboli menyesuaiakan continue menyelaputi themselves so that the entire embryo.

Emboli movement (creep) occurs adjacent to the embryo preformance. Takes place in the area - the area will mesoderm, notochord, and endoderm pre-chorda. Those regions move toward blastocoel. Emboli movement is divided into seven types, namely:

a. Involution, membellok movement inside.

b. Convergence, motion narrowing.

c. Invagination, mencekuk movement and folding of a layer.

d. Evaginasi, sticking a layer movement.

e. Delamination, a group of cells that memisahakan movement away from the main cell.

f. Divergence, the movement spread.

g. Extension, the movement spread.

• Amphioxus

Epiboli will take place in the entire ectoderm, along the anterior posterior body. Accompany the process of growing and melonjongnya embryos. Hypoblast invagination occurs in the median area adjacent to the dorsal sdabit, towards blastocoel, to meet denagn epiblast. Tues multiply that by extending hypoblast embryo axis. Area is called the blastopore invagination of hypoblast.

Involution will occur on the dorsal notochord of the crescent, in accordance with the movement towards the anterior hypoblast, so the notochord will be located in the dorso-median and just below the ectoderm. Extension will take place in the entire region toward the mesoderm dorso-median blastopore, in the lateral lip. Mesoderm eventually occupy both sides of the notochord would be located in the dorsal lip.

Amphibious

Epiboli lasts the ectoderm simultaneously with the occurrence of many-embolic processes, so that the entire embryonic ectoderm always menyelaputi. While it would extend limited neural ectoderm dorso-median area of ​​the embryo, along the anterior posterior axis, bebentuk shield, called a neural keeping or keeping nerve.

Chicken

At first there will be median thickening in areas on the caudal embryo. Thickening called the primitive streak. Formed in the posterior area pellucida, grew out of the cell - moving epiblast cells toward the posterior median, then the primitive streak in cells reproduce themselves. Almost half of the posterior area pellucida that will consist of pre-chorda, notochord and mesoderm, converge to the primitive streak and between hypoblast and epiblast berinvolusi.